The invention relates to a yarn feeder which can be used particularly for positive furnishing of yarns to textile machines.
The yarns to be furnished to individual yarn consuming stations of a textile machine can have quite different properties, depending on the material used, the twist, the yarn thickness, and other characteristics, and these properties also are found in the yarn feeder. For instance, cotton yarns, synthetic yarns, different processed or equipped yarns, such as smooth yarns, twisted yarns, kinky yarns, and so forth can behave differently. As a rule, yarn feeders should be capable of furnishing several or all of the yarns mentioned without difficulties.
Problems can arise here with yarns that shed dust, that have filaments protruding from the yarn, that carry a relatively large amount of sizing, or that in some other way leave behind or cause traces or deposits on parts of the yarn feeder. Deposits of fluff, which are located especially on the yarn feed wheel of a yarn feeder, can impair yarn travel and yarn feeding and in an extreme case can cause the yarn to tear.
From German Patent DE 35 01 944 C2, a yarn feeder is known that has a rotationally supported and driven yarn feed wheel, which is formed by a yarn storage drum provided with a plurality of conical regions. A first conical region with a cone angle of 150 forms the yarn inlet region. This is adjoined by a further yarn inlet region with a cone angle of 14, which is adjoined by a practically cylindrical yarn storage region.
The diameter of the yarn windings resting on the yarn inlet region decreases in the axial direction of the relatively long yarn inlet regions. The incoming yarn pushes the windings, already located in the inlet regions, in the axial direction, causing them to migrate toward the storage region, and the yarn tension in the individual windings can then vary. The yarn properties affect this process.
From German Patent DE 33 26 099 C2, a yarn feeder is also known which also has a rotatably supported and rotationally driven yarn feed wheel. The yarn feed wheel has a yarn inlet region, defined by two cones adjoining one another, and a yarn storage region adjoining it via a step that in one version is cylindrical or ribbed. The yarn feed wheel can be in a single part or in multiple parts. From the same patent, it is also known to provide the yarn inlet region and/or the yarn storage region with recesses, so as to bring about only a single uninterrupted support of the yarn in these regions. The storage drum in each version has a disk-like flange that extends in the radial direction on its lower end remote from the yarn inlet region and forms a step with the yarn inlet region.
A yarn feeder is also known from Published Taiwanese Patent Application, published under No. 165470, with a yarn feed wheel which has a conically tapering inlet region, an approximately cylindrical yarn storage region, and a yarn payout region, which is formed by a portion embodied on the order of a pulley. At the transition from the storage region to the pulley-like portion, there is a conical transitional region. In the yarn storage region, a flutelike groove extending around the circumference is provided, which divides the yarn storage region into individual contact faces separated from one another.
The yarn feed wheel has a relatively complicated shape.
From Taiwanese Utility Model published under No. 314077, a yarn feeder is known that has a rotationally symmetrical yarn feed wheel which is embodied in one piece and has a yarn inlet region, a yarn storage region, and a yarn payout region. The yarn inlet region with a convex curvature follows an annular cutout from a torus, while the yarn storage region is approximately cylindrical. Adjoining the yarn storage region, the diameter of the yarn feed wheel gradually increases, resulting in a conical region with a cone angle of a few degrees.
The incoming yarn presses the yarn windings located on the cylindrical yarn storage region axially away from the inlet region during operation of the yarn feeder, and the static friction of the entire package has to be overcome.
From German Utility Model DE 296 16 525 U1, a yarn feeder is known with a yarn feed wheel made up of multiple parts, in which the yarn inlet region, the yarn storage region and the yarn payout region are formed by axially extending ribs, whose outer profile defines the contour of the yarn feed wheel. The ribs are held at their ends on end disks.
The package advancement on the yarn feed wheel brought about by the incoming yarn is limited to the narrow ribs in the yarn inlet region. The ribbed yarn payout region can lead to turbulent yarn travel.
From European Patent Disclosure EP-A 0 568 762, a yarn feeder is known that has a yarn guide drum which has a conical upper and lower edge, and between them has a cylindrically embodied yarn storage region. Over a certain portion of its axial length, the cylindrical yarn storage region is provided with slots, which are covered by the yarn package. Between the slots, there are lands whose outer contour is located on the cylindrical surface that is defined by the cylindrical storage region.
The yarn wound as a package onto the storage region rests on the edges of the lands, which can be disadvantageous in the case of delicate yarns.
Regardless of wear, different yarns and packages behave differently. Differences exist particularly between smooth yarns and yarns with filaments, in which individual windings rest on filaments of adjacent windings and can firmly clamp them. It will be appreciated, however, that the usefulness of yarn feeders should not be limited to certain yarns.
With this as the point of departure, it is the object of the invention to create a yarn feeder whose operation properties are largely independent of the nature of the yarn. This object is attained by a yarn feeder having a yarn feed wheel with a special geometry that facilitates the feeding and payout of yarn onto and from the yarn feed wheel.
The yarn feed wheel of the yarn feeder may have a wearproof surface, which is applied to a carrier of lesser hardness, such as a metal body, or it may entirely comprise these substances. The yarn feed wheel is preferably in one piece, which makes economical manufacture possible. The yarn feed wheel is preferably embodied without through openings in its yarn inlet region, storage region and yarn payout region, so that it surrounds a closed interior. The storage region is preferably embodied as a substantially closed surface configuration, in which as needed relatively small openings spaced apart from the yarn bearing regions can also be provided. Fluff or other deposits are then unable to stick in the openings over which the yarn sweeps and impede yarn travel. The abrasion resistance prevents the development of scratches or bumps or other traces of wear, which over the long term could interfere with proper operation, and especially the even advancement of the package.
In the yarn feed wheel with a ceramic surface, it has also proved to be advantageous to embody the yarn inlet region and the yarn payout region as a closed surface, preferably with a circular cross section at every point. Conversely, the yarn storage region can have a cross section other than the circular form. For instance, the cross section can be defined polygonally, and either straight or indented edges may be provided between the individual, somewhat rounded corners of the polygon. The indented edges may be concave or intermittently concave and convex.
Such a design prevents the deposition of continuous rings of fluff or relatively large plugs of fluff in recesses, and the support of the yarn package remains concentrated on individual edge regions of the yarn segment. This facilitates the axial displacement of the package, so that the package can be displaced in controlled fashion even with different yarns or threads. Even if the bearing faces become worn somewhat, conditions are not fundamentally changed, and the yarn feeder functions reliably. Because the package is laid on in the storage region only in striplike bearing regions, it is easier to feed yarns that have many filaments, in particular. Because of the package advancement, filaments that get under the package can be firmly clamped only in the bearing regions. The outgoing yarn thus is easily separated from the package. If filaments that have caught remain under the package and are thus drawn off from the yarn, still no cohesive rings of fluff are created on the yarn feed wheel.
The cooperation of a closed structural shape of the yarn feed wheel with striplike contact faces in the storage region and closed, smooth surfaces in the inlet region and the payout region, which merge with one another without shoulders edges or steps, makes for good advancement with little static friction, and the deposition of fluff and the formation of rings of fluff as well as generation of wind or air flow by the yarn feed wheel are avoided.
The yarn feed wheel, which comprises or is coated with ceramic or some other of the aforementioned hard substances can be embodied in one piece, which makes it possible for the entire surface swept by the yarn to be seamless. The yarn can thus travel unhindered, and there is hardly any risk that it might get caught at a seam, for instance.
Advantageously, the yarn touches the surface of the yarn feed wheel uninterruptedly in the yarn inlet region and is guided in such a way that the yarn payout region can be swept clean by the yarn. This is attained by disposing the yarn payout eyelet or some suitable guide device at a radial spacing from the pivot axis of the yarn feed wheel and below a plane defined by the lower edge, with the result that the yarn rests on the yarn feed wheel, including at the transition from the storage region to the payout region, until it finally separates from the package.
The hub of the yarn feed wheel can be embodied integrally with it. The yarn feed wheel is then a single one-piece component. This makes manufacture and production simpler. The hub is preferably formed by an end wall of the yarn feed wheel.
If the yarn feed wheel comprises an optionally coated metal, such as aluminum, then it is considered advantageous to produce the yarn feed wheel by deep drawing or by shaping from a solid block. The yarn inlet region, the yarn payout region and preferably also the face-end wall or hub of the yarn feed wheel are embodied from a blank in one or more successive shaping steps. If needed, the shaft that carries the yarn feed wheel can also be embodied integrally with the yarn feed wheel.